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RE: ACI 318 App D, and wedge anchors - More confusion

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Suppose I determine that a particular post installed anchor has an ultimate shear capacity of 1,640 lbs based on ACI Appendix D. The anchor is in a high seismic area and the anchor is not ductile.

 

1. How are the 0.75 (ACI D.3.3.3) and 2.5 (CBC 1908.1.16) factors combined for seismic loads?

Would the allowable capacity for seismic loading be (0.75)(1,640/1.4)/2.5 = 351 lbs?

The 0.75 factor is due to ACI D.3.3.3 and the 2.5 factor is due to 2007 CBC section 1908.1.16.

The way I read 1908.1.16, it is “either/or” relative to the 0.75 and the 2.5 factors.

In other words, if the anchor is ductile, would the (ASD) capacity be (0.75)(1,640/1.4) = 879 lbs.?

If the anchor is not ductile, would the (ASD) capacity be (1,640/1.4)/2.5 = 469 lbs?

 

2. Are these factors still used when comparing the capacity of the anchor to the demand induced by wind loading?

In other words, would the allowable capacity of the anchor in resisting wind loads be (1,640/1.6) = 1,025 lbs?

(note the absence of the 0.75 and 2.5 factors).

 

The more I read, the more confused I become.

 

T. William (Bill) Allen, S.E.

ALLEN DESIGNS

Consulting Structural Engineers
 
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